Hardly are there any "extremist" leftists in the US (never heard of any advocating for a revolution) and any calls for censorship come from a tiny minority of Tumblr–like social justice warriors.

Agreed that the number of extremist leftists are small in the US. Unfortunately, many of those "Tumblr-like social justice warriors" work in the academia, media and government and wield disproportionate power. And if you haven't heard of any talk of revolution, you must have lived in seclusion somewhere in the woods and missed out on 3 years of post-Trump hysteria. Lucky you.

Where is the seizing of the means of production? Even nationalization of companies is a no–no. Political discourse is radically liberal economically in the US (thanks, Mr. Reagan) so there's really little leftism in the left.

As long as somebody censors anything, tor has merit as you choose what you see and not some faceless nobody.